This invention relates primarily to vehicle testing in which the vehicle wheels are supported on, and rotate with, rollers in a test bed. The concepts are equally applicable to situations in which the roller drives the wheel, such as brake analyzers or other motoring dynamometers, and to situations in which the wheel drives the roller, such as absorption dynamometers.
Problems encountered in such vehicle test beds are the slow start-up and wheel spinning which occur if the tires of the vehicle being tested are wet, and also if they have significant amounts of other foreign material, such as powdered material picked up from the road surfaces.
It is important that the means provided for removing water (and other materials) to reduce start-up time not create another problem in the form of excessive sound generation or noise.
Applicant is not aware of any prior art which shows helically grooved rollers which are designed to improve surface friction by using the grooves to remove water and other foreign materials. The prior art known to applicant does include rollers having surface grooves, or ridges, parallel to the axis of the rollers; and tire-contacting surfaces, grooves, or ridges, parallel to the direction of tire rotation. The grooves, or ridges, parallel to the roller axes tend to create excessive noise at high turning speeds. They are satisfactory for low-speed dynamometers, but not for high-speed dynamometers. Tire-contacting grooves, or ridges, which extend parallel to the direction of tire rotation do not provide a passage for lateral movement of the water to the sides of the tire, where it tends to leave the tire-roller contact surface in a spray.
I have found that greatly-improved results can be obtained by using helical grooves in the tire-engaging roller surfaces. In addition to providing a path for water removal, they seem to provide a "squeegee" effect on the tire which speeds up the water removal process.